The structure of 9-(3-bromo-6-chloro-2-hydroxyphenyl)-10-(2-hydroxyethyl)-3,6-diphenyl-3,4,5,6,7,9-hexahydro-2H-acridine-1,8-dione

The structure of a decaahydroacridine derivative with phenyl substituents at the 3- and 5-positions of the cyclohexenone rings is reported. An extensive range of O—H⋯O, C—H⋯O hydrogen bonds augmented by C—H⋯π(ring) hydrogen bonds an O⋯Br halogen bond and an unusual Br⋯π(ring) contact stabilizes the crystal packing.


Structural commentary
The title compound (I), consists of a hexahydro-2H-acridine ring system made up of a central dihydropyridine ring with an N-bound 2-hydroxyethyl substituent flanked by two cyclohexenone rings that carry phenyl substituents in the 3-and 5-positions, respectively (Fig. 1). The central C9 atom bears a 3-bromo-6-chloro-2-hydroxyphenyl substituent and the O2 0 hydroxy group forms an intramolecular hydrogen bond to the adjacent O8 carbonyl oxygen enclosing an S(8) ring. The C2 and C3 atoms of one cyclohexenone are disordered over two sites as is the C6 atom of the corresponding cyclohexenone. Their occupancy ratios refine to 0.521 (10):0.479 (10) for C2,C3 and 0.746 (9):0.254 (9) for C6. Only details of the major disorder components will be considered here. The central C9,N10,C11-C14 ring adopts a half-chair conformation and is inclined to the adjacent C1-C4,C11,C12 and C5-C8,C13,C14 rings at angles of 7.11 (18) and 21.64 (10) , respectively, so the hexahydro-2H-acridine unit is far from planar. The 3-bromo-6-chloro-2-hydroxyphenyl ring subtends an angle of 84.39 (6) to this central ring. The C1-C4,C11,C12 ring is best described as a severely flattened boat while the C5-C8,C13,C14 system is in a distorted half-chair conformation. The phenyl substituents on these outer cyclohexenone rings are inclined to their parent rings at angles of 76.87 (12) for C31-C36 and 86.27 (8) for C61-C66. The N-bound 2-hydroxyethyl substituent points away from the convex face of the hexahydro-2H-acridine system as does the 3-bromo-6-chloro-2-hydroxyphenyl substituent.

Supramolecular features
The crystal structure of (I) is supported by a full range of classical and non-classical hydrogen bonds and C-HÁ Á Á(ring) contacts, together with an intermolecular OÁ Á ÁBr halogen bond and an unusual C-BrÁ Á Á(ring) contact. Classical O16-H16OÁ Á ÁO8 hydrogen bonds, Table 1, form C(9) chains along the b-axis direction, linking the molecules in a head-to-tail fashion, Fig. 2. Chains also form along the a-axis direction through C65-H65Á Á ÁCg7 contacts, Fig. 3 Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
C(9) chains of molecules of (I) along b. In this and subsequent figures, hydrogen bonds are drawn as dashed lines.

Figure 3
Chains of molecules of (I) along a. C-HÁ Á Á contacts are shown as dotted green lines with ring centroids shown as coloured spheres.

Figure 1
The structure of (I) with ellipsoids drawn at the 50% probability level. For clarity only the major disorder components of the two cyclohexenone rings are shown. An intramolecular hydrogen bond is drawn as a dashed line.

Database survey
A search of the Cambridge Structural Database (Version 5.39 Nov 2017 with three updates; Groom et al. 2016) for an acri-dine ring system with a phenyl or substituted benzene ring on the central C9 atom gave 94 hits, 76 of which represented unique occurrences. The majority of these, 58, have two methyl substituents at the 3-and 5-positions of the ring system. However, three instances reveal a pair of methyl substituents on the 3-position only, with the remaining 15 structures having no additional substitution on either of the cyclohexenone rings. Interestingly, no structures were observed with phenyl substituents at the 3-or the 3-and 5positions of the hexahydro-2H-acridine ring system, emphasizing the uniqueness of the structure reported here. Refining the search to structures with CH 2 CH substitution on the acridine N atom reduced the hits to seven, four of which have hydroxyethyl substituents on N10 (Mohamed et al., 2013;Abdelhamid et al., 2016Abdelhamid et al., , 2014Abdelhamid et al., , 2011. Only one of the entries has a 2-hydroxypropyl N10 substituent , with pairs of methyl substituents on the 3-and 5-positions.

Synthesis and crystallization
The title compound was synthesized according to our previously reported method (Mohamed et al., 2013). Crystals suitable for X-ray diffraction were obtained by the slow evaporation method using ethanol/acetone (5:1) as the solvent mixture. Yield, 79%; m.p. 451 K.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All H atoms were refined using a riding model with d(C-H) = 0.95 Å for aromatic, 0.99 Å for methylene and 1.00 Å for methine H atoms, all with U iso = 1.2U eq (C). The C2 and C3 atoms in the C1-C4,C11,C12 cyclohexenone ring and atom, C6, in the corresponding C5-C8,C13,C14 ring are disordered over two positions. Their Chains of molecule of (I) formed by C-HÁ Á ÁO hydrogen bonds, C-BrÁ Á Á and OÁ Á ÁBr contacts, dotted green lines.

Figure 6
Overall packing of (I) viewed along the a-axis direction.

Figure 4
Double chains of molecules of (I) along the ab diagonal.
occupancies were refined to sum to unity with the disordered atoms of the different rings allowed to refine separately. The occupancies converged to ratios of 0.521 (10): 0.479 (10) for C2 and C3 and 0.746 (9): 0.254 (9) for C6. Positions of the hydrogen atoms on adjacent methylene groups and phenyl rings were assigned taking this disorder into account but a somewhat close H15AÁ Á ÁH5C contact was still observed. One reflection with F o >>> F c , was omitted from the final refinement cycles.   Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. One reflection with Fo >>> Fc was omitted from the final refinement cycles.